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Applied Research Of Micro-nano Materials For Lithium-sulfur Batteries Wity Hihg Capacity And Stable Cycling Performance

Posted on:2017-07-14Degree:MasterType:Thesis
Country:ChinaCandidate:L WangFull Text:PDF
GTID:2311330488978513Subject:Chemistry
Abstract/Summary:PDF Full Text Request
Employing sulfur as cathode material,lithium-sulfur batteries?LSBs?are one of the most promising candidates for next-generation rechargeable batteries for their high theoretical capacity,low cost,and environmental friendliness.However,with its aiming at commercial practical application,there exist two main issues to be settled down,?:element sulfur is insulative;?: presence of “shuttle effect”of the lithium polusulfides?LiPSs?formed in charging/discharging could dissolve in the electrolyte and shuttle back and forth between the anode and the cathode.It is therefore crucial to improve the conductivity of the sulfur cathode and maintain/reuse the soluble LiPSs.In this thesis,sulfur,nitrogen co-doped graphene and boron doped graphene were developed in high-temperature pyrolysis methode.Based on conventional cathode with sulfur loaded in carbon nanotube,the doped graphene were plunged in on the surface of cathode as the interlayer in a facile double-coating methode.The main contents are as follows:?1?Sulfur,nitrogen co-doped graphene?SNGE?was fabricated through pyrolysis of thiourea and graphene oxide?GO?.Then a facile double-coating of the SNGE interlayer on the surface of PCNT-S cathode was carried out to produce PCNT-S@SNGE cathode.Results were obtained that,introduction sulfur and nitrogen atoms into the graphene skeleton were realized;benefiting from functionalities of physical interception and chemical absorption of LiPSs and improved conductivity granted by the SNGE interlayer,“shuttle effect” was effectively restrained and increased utilization of active sulfur material were achieved for the cathode;notably,capacity retention of 1463 mAh g-1 at0.25 C and 130 mAh g-1 at 40 C were achieved in rate performance,and stable cycling performance over 1000 charge/discharge cycles at high rates of 8C and 10 C were obtained,with superior decay rate of 0.01% and0.03%,respectively,exhibiting excellent high-power out-put performance.?2?Boron doped graphene?BGE?was fabricated through pyrolyzation of boric acid and graphene oxide?GO?.Then a facile double-coating of the BGE interlayer on the surface of CNT-S cathode was carried out to produce CNT-S@BGE cathode.Research results were obtained that boron atoms were introduced into graphene skeleton,and improved the rate performance of 490 mAh g-1 capacity at 10 C andcycling performance of 250 mAh g-1 capacity over 900 cycles at 10 C were achieved.
Keywords/Search Tags:graphene, nitrogen, sulfur co-doping, boron doping, interlayer structural material, lithium sulfur battery
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